Re: [PATCH 0/4] Compile kernel with -fwhole-program --combine

From: David Woodhouse <dwmw2@infradead.org>
To: Rob Landley <rob@landley.net>
Cc: linux-kernel@vger.kernel.org, linux-tiny@selenic.com, devel@laptop.org
Subject: Re: [PATCH 0/4] Compile kernel with -fwhole-program --combine
Date: Fri, 25 Aug 2006 21:35:15 +0100	[thread overview]
Message-ID: <1156538115.3038.6.camel@pmac.infradead.org> (raw)
In-Reply-To: <200608251611.50616.rob@landley.net>

On Fri, 2006-08-25 at 16:11 -0400, Rob Landley wrote:
> BusyBox has been doing this for months now: "build at once" is one of our 
> config options.  I'd like to point out that gcc eats needs several hundred 
> megabytes of ram to do this and you have no useful progress indicator between 
> starting and ending.  But the result is definitely smaller.

It isn't that bad when you're only building a few files at a time -- I
wouldn't suggest doing it for the whole kernel.

And you get a nice progress indicator at the moment -- a new warning
about global register variables every time it eats a new file, due to
GCC PR27899 :)

> We also tell the linker "--sort-common --gc-sections" which may or may not 
> apply here...

We want --gc-sections (which requires -ffunction-sections
-fdata-sections to be useful) but that's a separate issue. We were doing
it a long time ago for the FR-V kernel; Marcelo has been looking at it
recently for other architectures.

-- 
dwmw2